Electrophotographic apparatus



June 18, 1968 A. J. STANTON 3,388,688

ELECTROPHOTOGRAPHIC APPARATUS Filed June 30, 1966 2 Sheets-Sheet UnitedStates Patent 3,388,688 ELECTROPHOTOGRAPHIC APPARATUS Arthur J. Stanton,Warrensville Heights, Ohio, assignor to Harris-Intertype Corporation,Cleveland, Ohio, a

corporation of Delaware Filed June 30, 1966, Ser; No. 561,849 8 Claims.(Cl. 118-637) ABSTRACT OF THE DISCLOSURE A developer unit for use withan electrophotographic apparatus wherein a sheet bearing anelectrostatic image on one side is directed downwardly by guide elementsinto a liquid developer and then undergoes a change in direction so thatthe sheet leaves the developer traveling in a generally upwardlydirection. No relative movement occurs between the image side of thesheet and any surface or component of the developer unit. Those surfacesin contact with the image side of the sheet are electrically insulatingand are moved at the same velocity as the sheet to prevent distortionofthe electrostatic image. Only the leading and trailing edges of thesheet are allowed in sliding contact with the stationary guide elementswithin the developer unit.

This invention relates to a developer unit for an electrophotographicapparatus and more particularly to such a unit for use in developingsheet members in a liquid developer wherein the sheet bearing anelectrostatic latent image is immersed and passed through the developerin such fashion that the surface thereof having the image thereon isfree from contact with any stationary surface thereby to avoid blurring,streaking or marring of the developed image. I

In the operation of an electrostatic photographic device, such asdescribed in copending application Ser. No. 346,718, filed Feb. 24,1964, a sheet of paper is first advanced through a charging stationwhere the sheet is charged and then advanced into an exposing stationwhere a light image of an original document is projected thereon tocause formation of an electrostatic latent image charge corresponding tothe original. The sheet is thereafter advanced into and through adeveloper liquid containing charged marking particles in an electricallyinsulating carrier liquid wherein the marking particles are deposited ascontrolled by the latent image and form a visible copy of the original.As the sheet leaves the developing station, excess carrier liquid isremoved by passing the sheet between a pair of rollers acting as asqueegee and the sheet thereafter travels through a heating station toremove the remainder of the liquid and to effect substantially permanentadhesion of the marking particles to the surface of the image bearingsheet member.

While the sheet is in contact with liquid developer, relative motionbetween the image side of the sheet and any portion of the developerunit may cause the image to be distorted or smeared during development.As the sheet bearing the latent image is passed through the liquiddeveloper in the preferred embodiment of the invention, the sheetundergoes a change in direction, from a generally vertically downwardmovement into the developer to a generally vertically upward movementout of the developer unit. This change in direction is eifected whilethe sheet is in liquid developer by guiding the sheet through thedeveloper unit but at the same time substantially eliminating anyrelative sliding contacting movement between the image side of the sheetand any surface or component of the developer unit.

The present invention therefore relates to a developer Patented June 18,1968 unit wherein the sheet is directed into the developer liquid, andduring contact with the developer, any sliding contact between the imageside of the sheet and any part of the unit is eliminated. The developerunit receives a sheet from the exposing station, and includes guideelements to direct the sheet into the developer and to guide the imageside of the sheet away from any stationary surface. Some of the surfacesin contact with the image side of the sheet may be electricallyinsulating and are moved at the same linear velocity as the surface ofthe sheet. Only the leading and trailing edges of the sheet are allowedin sliding contact with the guide elements of the developer unit whilethe image side of the sheet is kept free from sliding contactingmovement with the stationary components of the developer unit.

Accordingly, it is an object of this invention to provide a developerunit for use in an electrophotographic apparatus wherein a sheet bearingelectrostatic latent image is so guided while in a liquid developer thatsliding contacting movement between the image side of the sheet and anypart or component of the developer unit is Substantially eliminated.

It is another object of this invention to provide a developer unitincluding fixed and rotatable guides so arranged that a sheet bearing anelectrostatic latent image is lifted away from all stationary surfacesso that the electrostatic latent image on the sheet is not streaked ormarred by any rubbing with stationary parts as the sheet is guidedthrough the developer.

It is another object of the present invention to provide a compactdeveloper unit of the type described for developing an electrostaticlatent image on a sheet membet with a liquid developer, the developerunit including a generally U-shaped developing channel at least part ofwhich is below the level of the liquid developer, the channel beingformed by rotatable elements, fixed elements in sliding contact with thenon-image side of the sheet at spaced intervals, and additional fixedelements functioning as guides in contact with only the leading andtrailing edges of the sheet thereby substantially eliminating anysliding contact of the image side of the sheet with any element as thesheet travels through the channel.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

In the drawings:

FIG. 1 is a front elevational view of a liquid developer unitconstructed according to this invention with some of the component partsbroken away to reveal other parts situated therebehind;

FIG. 2 is a cross-sectional view taken along line 22 in FIG. 1;

FIG. 3 is an end view of the developer unit particularly showing thegearing arrangement usedto drive the unit; and

FIGS. 4-10 are simplified views of portions of a developer unit inaccordance with this invention showing the path taken by a sheet ofpaper as it passes through the unit.

Referring to the drawings, which show a preferred embodiment of thepresent invention, the developer unit in FIGS. 1 and 2 is mounted on abase 10 and includes a tank 11 having a pair of vertically mounted endwall members 12 and 13 and a pair of upwardly sloping diverging wallmembers 14. A pair of end plates 15 and 16 removably support thedeveloper mechanism within the tank 11; Spacer rods 18 and 18 aresecured to the end plates to provide rigidity and support. A liquiddeveloper may be introduced into the tank through aninlet pipe 20extending through the wall member 12, and the developer may be removedthrough a discharge pipe 21 mounted at the bottom of the tank andextending through the wall member 14. The normal level of the developerfluid in the tank is shown by a dashed line 22 in FIG. 2.

An agitator mechanism 23 is provided in the tank to insure a uniformdispersion of marking particles throughout the electrically insulatingcarrier liquid. This agitator consists of four paddle wheels 25 keyed toa hub 26, and mounted on shaft 27 which rotates in end plates and 16.The hub 26 is locked to the shaft 27 by a set screw 28. The agitatorpaddles are enclosed within a deflector assembly 30 and consist of acurved deflect-or plate 31 and three substantially identical plates 32,33 and 34 each mounted at their ends by screws 35 to a pair of supportplates 36, only one of which is shown in FIG. 2. Each of the supportplates 36 is secured to one of the end plates 15 and 16 by screws (notshown), and the agitator mechanism is positioned between the supportplates 36. Each of the deflector plates 32-34 is provided with aplurality of openings as shown in FIG. 1, through which the liquiddeveloper may freely pass, thus allowing the agitator to mix anddistribute the marking particles continuously through the carrierliquid.

As shown in FIG. 2, each support plate 36 includes a plurality of spacedflat faces on the lower portion thereof which receive one of the plates32-34 so that a portion 32a-34a of each plate 32-34, respectively,extends beyond the periphery of the support plate as shown. The plates32-34 extend across the width of the developer unit as shown in FIG. 1.Curved deflector plate 31 also includes an extending portion 31a whichlikewise extends beyond the periphery of support plates 36. Theextending portions 31a-34a of plates 31-34 are adapted to contact thenonimage side of the sheet in sliding contacting relationship at thespaced intervals along the length of the sheet. Since these extendingportions are aligned at right angles to the path of sheet travel, onlyline contact is made between the sheet and extending portions of theplate with the result that the non-image side of the sheet issubstantially free of guide or streak marks.

A sheet of paper having an elctrostatic latent image thereon is directedinto the developing unit through guides 40 and 41 which extend acrossthe unit and the leading edge of the sheet then received between adriven roll 42 mounted on a shaft 43 and pressure roll 44 which ismounted on shaft 45. The image side of the sheet is positioned tocontact the pressure roll 44. The shaft 43 extends through end plate 16where it is driven through a suitable gearing arrangement, later to bedescribed. The pressure roll 44 is journalled between lever arms 46,each of which is pivoted on pin 47 and urged into engagement with thedriven roll 42 by springs 48. While only one lever arm assembly isshown, it is understood that both ends of the shaft 45 are similarlymounted.

As the sheet is fed into the developer unit, the leading edge thereof ispicked up by rolls 42 and 44 which drive the sheet beneath the level ofthe liquid developer. The rolls 42 and 44 are arranged so that the sheettends to leave the rolls 42 and 44 in a direction perpendicular to animaginary line drawn between the centers of theroll. Thus, as theleading edge of the sheet leaves the nip of rollers 42 and 44 it will bedirected against deflector plate 31 as shown in FIG. 4. As the sheet isadvanced further, the leading edge thereof will pass over the edgeportion 31a of deflector plate 31, and come into contact with aplurality of curved cam blades 51 which serve as a first camming means.

Each of the cam blades includes a concave shaped camming surface whichfaces the agitator mechanism 23 and the cam blades are held in alignmentby pair of shafts 52 and 53 which extend between the end plates 15 and16. The cam blades are spaced from each other by spacers 54 between eachcam blade. The blades, which form first camming means are so arrangedwith respect to deflector plates 31 and 32 that the leading edge of thesheet plate is directed toward a deflector roll 57.

The deflector roll 57, mounted on shaft 58, is positioned to receive theleading edge of the sheet from the cam blades 51 and dire-ct it toward asecond set of cam blades 62. The shaft 58 is journalled at one end inend plate 15, while the other end of the shaft passes through the otherend plate 1-6 where it is so rotated that the tangential velocity of theroll 57 is the same as the linear velocity of the sheet at the point ofcontact thereby preventing relative motion beween the sheet and theroll. This is necessary in order to prevent blurring, streaking andmarring of the image side of the sheet. As an additional precautionagainst unwanted marking of the sheet, a scrubber assembly 61 consistingof a flexible pad of a spongy material is mounted in sliding contactwith the deflector roll 57 at a point remote from the point of contactwith the sheet. The scrubber functions to clean the roll and to removeany deposit of marking particles which may be accumulated thereon.

The second set of cam blades 62 function as a second camming means andeach blade is essentially the same as blades 51 except that the lowerends are rounded, as shown, to permit easy passage of the leading edgethereon. Each cam blade 62 is so mounted that the camming surface facesthe agitator mechanism 23, and the cam blades 62 are arranged to makesliding contact with the leading edge of the sheet as it passes throughthe developer tank. Each blade 62 is mounted on shafts 63 and 64 andmaintained in alignment by spacer members similar to that shown with thefirst set of cam blade-s 51.

The second set of cam blades guides the leading edge of the sheet torolls 70 and 71 mounted for rotation on shafts 72 and 73, respectively.Roll 70 is driven and roll 71 is a pressure roll journalled between apair of levers 74 pivoted on pin 75 and urged into engagement with thedriven roll by a spring 76. The spring 76 will create sufficientcompression between the pressure roll and the driven roll to remove asubstantial portion of the developed carrier liquid as the sheet movesupwardly out of the developer.

The rolls 70 and 71 are arranged in such a manner that the image side ofthe sheet will be lifted away from the surface of the second set of camblades 62 as the sheet moves onto the nip of rolls 70 and 71 and thus,the nonimage side of the sheet will be urged against the deflectors 33and 34 when the sheet begins to pass between both rolls 70 and 71.

A scrubber pad 78 is mounted on the tank wall 14 and runs the length ofthe pres-sure roll 71 to clean it and to remove any accumulation ofmarking particles which maybe deposited thereon. A further scrubber 79,mounted on end plate 36, extends the length of roll 70 and removes anydeposit of marking particles therefrom. A portion of each of scrubbers78 and 79 is always in contact with the liquid developer so that,through capillaiy action, these scrubbers are maintained moist and readyfor use, even though the developer unit may stand idle for periods oftime.

The sheet is then directed upwardly between the guides 80 and 81 whereit then passes to the drying station, as described in the abovementioned copending application. A switch 83 is mounted on the plate 81and has an actuating arm 84 extending into the space between the guides80 and 81 to sense the presence of a sheet and is used to control theoperation of the drying station.

Since relative movement between the sheet and any part within thedeveloper unit would cause the blurring or streaking of theelectrostatic image, it is necessary to insure that the moving surfaceswithin the tank which come in contact with the sheet have the sametangential velocity at the point of contact with the sheet as the linearvelocity of the sheet. Therefore, each of the rollers 44, 57 and 71 isrotated at a precisely controlled speed.

Referring now to FIGS. 1 and 3, power to the developer assembly torotate these moving surfaces is obtained from a motor 87 and throughgears 88 and 89 to drive gear 90. Gear 90 is not only in engagement withgear 89, but also has a portion in engagement with the large gear 91.Gear 89 is fixed to the shaft 72 which causes the driven roll 70 to movethe sheet upwardly out of the developer tank. The large gear 91 is fixedto shaft 27 and causes the agitator blades to rotate at a relativelyslow speed, and at the same time drives gear 92 fixed to shaft 58 andthe deflector roll 57, and also rotates driven roll 42 through a pair ofgears 93 and 94, the last named gear being fixed to shaft 43.

The non-image side of the sheet is engaged by the driven rolls 42 and 70which insures that the pressure rolls 44 and 71 will rotate at exactlythe same speed as the image side of the sheet since the pressure rollsare actually driven through the sheet itself. The deflector roll 57,being geared to the sheet moving mechanism, is also rotated at preciselythe correct speed to insure absence of relative movement between theimage side of the sheet and that roll.

Referring now to FIGS. 4-10 for a more complete understanding of theoperation of this invention, a sheet 100 containing an electrostaticimage on side 101 formed to correspond to the image on an originaldocument is directed between the guides 40 and 41. The sheet is receivedbetween the rollers 42 and 44 which are arranged to direct the sheetinto the tank assembly where the leading edge will engage the deflectorplate 31 (FIG. 4). As the sheet continues to move into the tank, theleading edge slides down the deflector plate 31 until it contacts thecamming surface of the blade members 51 (FIG. 5) which direct theleading edge toward the deflector roll 57 (FIG. 6). At this relativeposition, the non-image side 102 of the sheet is in sliding contact withthe lower edge portion 31:; of the deflector plate 31. As the deflectorroll 57 receives the leading edge of the sheet 100, the image side ofthe sheet will be lifted away from the camming surface of the first setof cam blades 51 (FIG. 7) so that the image side of the sheeet 100 willbe free from sliding contact with any stationary surface. As pointed outpreviously, roll 57 is rotated with a tangential velocity which is thesame as the linear velocity of the sheet moving through the tank.

The leading edge of the sheet will then make sliding contact with thesurface of the second set cam blades 62 (FIG. 8) and be directedupwardly out of the developer solution. As the sheet continues to moveupwardly, the leading edge enters the nip of rollers 70 and 71 (FIG. 9),and due to the orientation of the rolls, the sheet is lifted off of thesurface of the second set of cam blade means 62 to eliminate againrelative movement between the sheet and any stationary surface. Rolls 70and 71, in addition to acting as drive or pull through rolls, alsoremove carrier liquid as previously noted. The leading edge of the sheetcontinues upwardly through the guide plates 80 and 81 and causes theactuating arm 84 of the switch to move and to commence the drying cycle.

As shown in FIG. 9, the non-image side 102 of the sheet engages thelower edge portion 31a of the deflector plate 31 and the extendingportion 32a34a of deflectors 32-34, respectively. In this relativeposition of the sheet there is a portion of the sheet which has not yetentered the nip of rolls 42, 44. While the image side of this portion ofthe sheet may contact guide 41, no streaking or marking has beenobserved because the guide 41 is out of the developer liquid. The imageside of the sheet which is in the developer, however, is prevented fromcoming in contact with any stationary surface.

Rolls 70 and 71 are so arranged along the path of sheet travel that asthe leading edge of the sheet enters the nip between them, rolls 42 and44 are still driving the sheet. Thus, the linear distance along the pathof travel between rolls 70, 71 and 42, 44 is less than the length of thesheet.

As the trailing edge of the sheet is released by rollers 42 and 44, itwill fall and contact the upper portion of the first set cam blades 51,as shown by the dotted line (FIG.

10), which provide support for the remainder of the sheet. Since onlythe trailing edge of the sheet follows the camming surface of the camblades, there is no sliding contact between the image side of the sheetand the cam blades 51. Thus, only the leading edge and the trailing edgeof the sheet is in sliding contact with any stationary surface beneaththe level of the liquid developer, and no smearing, streaking or marringof the image will therefore result as the sheet passes through thedeveloper tank.

Thus, the developer unit of the present invention includes a tank, andthe first set of cams cooperate with the opposed deflector plates toform a generally downwardly extending leg of a sheet receiving channelwhile the second set of cam plates and the opposed deflector plates forman upwardly extending leg of the channel. Positioned in the path ofsheet travel and between the first and second set of cam plates is aroller which functions to lift the leading edge of the sheet and advanceit to a second sheet of cam plates. In this way, there is no relativesliding movement between the image side of the sheet and any portion ofthe developer unit which is beneath the level of the liquid developer,and thus, streaking or marking of the image side of the sheet duringdevelopment is substantially eliminated.

While the form of apparatus herein described constitutes a preferredembodiment of the invention, it is to be understood that the inventionis not limited to this precise form of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. A unit for developing electrostatic images on a sheet with a liquiddeveloper comprising:

a tank adapted to contain a liquid developer including marking particlesin an electrically insulated carrier liquid;

means for receiving a sheet having an electrostatic latent image thereonand for directing the sheet into said tank;

first camming means positioned in said tank in facing relation to theimage side of the sheet for receiving the leading edge of the sheet insliding contact as it moves through said tank;

a deflector roll mounted in said tank for receivirig the leading edge ofthe sheet from the first camming means and for lifting the image side ofthe sheet off the surface of said first camming means thereby preventingsliding contacting movement between the image side of the sheet and saidfirst camming means, said roll having a tangential Velocity the same asthe linear velocity of the sheet to prevent relative movementtherebetween;

second camming means positioned in said tank in fac ing relation to theimage side of the sheet for receiving the leading edge of the sheet insliding contact after it passes said deflector roll and for guiding thesheet upwardly and out of said tank;

means for receiving the sheet from said second camming means andadvancing it upwardly out of said tank,

said last named means so arranged that the image side i of the sheet islifted away from the surface of said second camming means therebypreventing relative sliding contacting movement between the image sideof the sheet and said second camming means; and deflector means inspaced opposed relation to said first and second camming means to formtherewith a sheet receiving channel, said deflector means comprising aplurality of blade members having edge portions mounted at right anglesto the path of sheet travel and adapted to receive in sliding contactthe nonimage side of said sheet. A 2. The developer unit defined inclaim 1 further including a scrubber means mounted adjacent to and insliding contact with said deflector roll for cleaning said roll andremoving deposits of marking particles therefrom.

3. The developer unit as defined in claim 1 wherein said first andsecond camming means includes a plurality of curved blade membersmounted with the edge portions thereof positioned to receive in slidingcontacting movement the leading and trailing edges of said sheet therebyproviding a minimum area of contact therewith.

4. A unit for developing electrostatic images on a sheet with a liquiddeveloper comprising:

a tank adapted to contain a liquid developer including marking particlesin an electrically insulating carrier liquid;

means for receving a sheet having an electrostatic latent image thereonand for directing the sheet into said tank;

first camming means positioned in said tank in facing relation to theimage side of the sheet for receiving the leading edge of the sheet insliding contact as it moves through said tank;

a deflector roll mounted in said tank for receiving the leading edge ofthe sheet from the first camming means and for lifting the image side ofthe sheet oil the surface of said first camming means thereby preventingsliding contacting movement between the image side of the sheet and saidfirst camming means, said roll having a tangential velocity the same asthe linear velocity of the sheet to prevent relative movementtherebetween;

second camming means positioned in said tank in facing relation to theimage side of the sheet for receiving the leading edge of the sheet insliding con tact after it passes said deflector roll and for guiding thesheet upwardly and out of said tank; and

means for receiving the sheet from said second camming means andadvancing it upwardly out of said tank, said last named means soarranged that the image side of the sheet is lifted away from thesurface of said camming means thereby preventing relative slidingcontacting movement between the image side of the sheet and said secondcamming means, and including a driven roller in engagement with thenon-image side of the sheet with a tangential velocity the same as thelinear velocity of the sheet, a pressure roller in engagement with theimage side of the sheet, and spring means urging said pressure rollertoward said driven roller thereby squeezing said sheet therebetween asthe sheet moves upwardly out of said tank thereby causing the removal ofa substantial portion of said developer carrier liquid and promoting theadhesion of the deposited marking particles thereon.

5. The developer unit as defined in claim 4 further including a scrubbermeans mounted adjacent to and in sliding contact with said pressureroller for cleaning said roller and for removing any deposits of markingparticles therefrom.

6. The developer unit as defined in claim 1 further including rollermeans positioned to feed a sheet into said channel so that the leadingedge thereof contacts said deflector means, and second roller meanspositioned to receive a sheet from said channel so that the trailingedge of said sheet is in sliding relation with said second cammingmeans.

7. A unit for developing electrostatic images on a sheet with a liquiddeveloper comprising:

a tank adapted to contain a liquid developer including marking particlesin an electrically insulating carrier liquid;

means for receiving a sheet having an electrostatic latent image thereonand for directing the sheet into said tank including a driven feed rollin engagement with the non-image side of said sheet, a pressure roll inengagement with the image side of said sheet and spring biasing meansurging said pressure roll toward said driven roll thereby causing thepressure roll to rotate with a tangential velocity identical to thelinear velocity of said sheet so as not to distort the latentelectrostatic image on said sheet;

first camming means positioned in said tank in facing relation to theimage side of the sheet for receiving the leading edge of the sheet insliding contact as it moves through said tank;

a deflector roll mounted in said tank for receiving the leading edge ofthe sheet from the first camming means and for lifting the image side ofthe sheet oil the surface of said first camming means thereby preventingsliding contacting movement between the image side of the sheet and saidfirst camming means, said roll having a tangential velocity the same asthe linear velocity of the sheet to prevent relative movementtherebetween;

second camming means positioned in said tank in facing relation to theimage side of the sheet for receiving the leading edge of the sheet insliding contact after it passes said deflector roll and for guiding thesheet upwardly and out of said tank; and

means for receiving the sheet from said second camming means andadvancing it upwardly out of said tank, said last named means soarranged that the image side of the sheet is lifted away from the surface of said second camming means thereby preventing relative slidingcontacting movement between the image side of the sheet and said secondcamming means.

8. The developer unit as defined in claim 1 further including means foragitating the developer to insure an even dispersion of markingparticles throughout the electrically insulating liquid carrier.

References Cited UNITED STATES PATENTS 1,810,699 6/ 1931 Diescher118-429 XR 2,279,166 4/1942 Hudil et al.

3,186,325 6/1965 Belder -89 3,207,050 9/1965 Linberger 118637 XR3,249,088 5/1966 Ostensen 118-637 FOREIGN PATENTS 1,095,577 12/1954France.

1,135,294 8/1962 Germany.

CHARLES A. WILLMUTH, Primary Examiner.

PETER FELDMAN, Examiner.

